A wildfire grew by an estimated 200 square miles in 24 hours, blackening grazing land Sunday as it threatened thousands of southern Idaho homes and facilities at an Air Force training range, fire officials said Sunday.

Two large wildfires along the Nevada line combined Saturday to create the more than 880-square-mile blaze, which burned grass and brush and was less than a mile from a training range of Mountain Home Air Force Base.

No one has been seriously hurt, but the homes of about 7,500 people in the sparsely populated region were threatened, said Chuck Dickson, a fire information officer.

The fire was only about 15 percent contained, fire spokeswoman Pam Bierce said, and mandatory evacuations remained in effect for the town of Jarbidge, Nev. Evacuation warnings were lifted for residents of Murphy Hot Springs, Idaho.

The fire was near a Mountain Home training range that pilots use before heading to Iraq and Afghanistan. Dickson said tracking and radar facilities were at risk, but he was not sure what else was on the range.

"When a fire moves as quickly as this one does, pushed by the wind, it creates a very hot heat front," Dickson said. "That will impact even steel structures quite easily."

Officials with the base's security and fire departments on Sunday declined to comment about what type of facilities, if any, were at risk or how vulnerable they might be.

Dickson said that ranches in the area also were threatened, that a lot of grazing area had been lost, and that cattle likely had died in the fast-moving blaze. He didn't have an estimate of how many cattle were on grazing allotments within the fire's perimeter.

Dozens of other large fires were burning across the West on Sunday, primarily in Idaho, Nevada, Oregon and Utah, according to the National Interagency Fire Center.

Spotty rain helped firefighters battle a 28-square-mile blaze in central Utah on Sunday, but it remained just 15 percent contained, and residents of several small communities were told to leave.

The fire began Friday, and strong winds whipped the flames across areas full of dry vegetation, which ignited quickly and spread for miles.

Blazing heat and erratic winds had firefighters cautiously trying to pick where they could try to slow the blaze and not put themselves in too much danger. Flames shot 80 to 100 feet in the air overnight.

Gov. Jon Huntsman surveyed the area and asked for federal assistance, which was granted within two hours.

Ricardo Zuniga, a spokesman for the Federal Emergency Management Agency, said about 250 people had been affected by evacuation notices in Oaker Hills, Indian Ridge, Elk Ridge, Indianola and Holiday Oaks. A shelter was set up in Mount Pleasant, about 90 miles south of Salt Lake City, he said.

The cause was still under investigation. About 142 people were fighting the blaze, but only one hand crew, Hart said. Once conditions improved and more hand crews were available, Hart expected more progress.

"Everybody's short of resources throughout the West right now. Everybody is trying to make do with what they have," he said.

A fire in northern Idaho destroyed two residences and seven outbuildings Friday and Saturday, including properties at Boulder Creek Outfitters, a private hunting ranch.

"We lost our whole ranch," owner Tim Craig told the Lewiston Tribune. "We were all by ourselves. Nobody was there."

The blaze raced through tree crowns and shot out embers that created spot fires up to a mile away, said fire information spokesman Chuck Stanich.

The 31-square-mile fire, which was started by lightning, was 10 percent contained Sunday, Stanich said. People in communities north and east of the wildfire were encouraged to evacuate, he said.

Also Sunday, fire officials in California lifted the last of their evacuation warnings in northern Santa Barbara County, as crews continued making progress against the weeks-old wildfire in the Los Padres National Forest.

The blaze, which had burned some 31,000 acres, or about 48 square miles, since July 4, was 51 percent contained, with full containment expected on July 27, officials said.